Adjustable floating plug for tube drawing



E. ROTH 2,721,651

2 Sheets-Sheet l M m v f Y IN VEN TOR. v

EUGENE ROTH FLOATING PLUG FOR TUBE DRAWIN"`- Oct. 25, 1955 ADJUSTABLEFiled June 26, 1955 A MY. NN WN mN E. ROTH Oct. 25, 1955 ADJUSTABLEFLOATING PLUG FOR TUBE DRAWING Filed June 26, 1953 2 Sheets-Sheet 2EUGEN: ROTH IN VEN TOR;

United States Patent O ADJUSTABLE FLOATNG PLUG FOR TUBE DRAWING EugeneRoth, New York, N. Y.

Application June 26, 19535 Serial No. 364,465

13 Claims. (Cl. 20S- 7) This invention relates to improvements in meansfor drawing tubes and more particularly for drawing tubes with dies andfioating plugs.

The basic process in the manufacture of non-ferrous seamless tubinginvolves simultaneous reductions in the size of both the outsidediameter and wall thickness. In this manner, tubes of base or startingsizes can be worked down by one or more draws into finished tubes ofpre-determined dimensions. This process involves drawing or pulling thetube by suitable mechanical means through a circular ring or die ofsteel or carbide thus forming and sizing the outside diameter. This dieis securely held in a fixed position in the die head of the machine. Atthe samc time, a suitable steel or carbide tool inside the tube formsand sizes the inside diameter. It is apparent that proper control of thesize of both the outside and inside diameters produces the desired wallthickness. The tool which forms the inside diameter can vary in design.

In some plants a long red or mandrel of uniform diameter is placed inthe tube before drawing and travels with the tube through the die duringthe drawing operation. This is known as drawing with mandrels. After oneor more draws, the tube is stripped from the mandrel and a separateoperation is completed. This method is useful when heavy reductions ofwall thickness are desired or when proper lubrication of the inside ofthe tube is difficult. However, its use on non-ferrous metals is limitedbecause the stripping operation is an added expense and also distortsthe tube. ln addition, only relatively short tubes can be drawn sincethe mandrels must be longer than the drawn tube.

ln most plants drawing non-ferrous seamless tubing in straight lengthsthe inside diameter is formed by a cylindrical plug The plug is firmlyattached to a rod which extends through the back end of the tube andwhich in turn is securely attached to the frame of the machine(drawbench) by means of a threaded rod, which also allows changes in theposition of the plug relative to the die which forms the outside of thetube. The nose of the plug, over which tht-I drawing actually takesplace may be uniform in diameter (a straight plug) or may be tapered,usually about 0.015 in diameter per inch of length. In actual drawingthe inside diameter of the tube is formed by a relatively short portionof the nose, of the plug. Wear occurs on this area of the nose,resulting in a smaller inside diameter and heavier wall thickness. Bymeans of the threaded connection between the plug rod and the drawbenchframe, the position of the plug can be changed periodically to bring anew portion of the plug nose into use, thus restoring the desired sizeof the inside diameter. In this manner, wear can be distributed over theentire nose of a non-tapered or straight plug thus greatly increasingits life. When completely worn a straight plug may be machined to asmaller size or may be restored to its original size by chome plating.

With a plug having a tapered nose, distribution of wear 2,721,651Patented Oct. 25, 1955 ICC is also possible but the chief advantage ofthe tapered nose is that small variations in the size of the insidediameter can be produced by altering the position of the plug by meansof the threaded connection on the plug rod. The relative positions ofdie and plug control the inside diameter and wall thickness of the tube.The ability to control the wall thickness is a very important advantagenot only in meeting dimensional tolerances for wall thickness forfinished tubes (that is during the last draw) but also in maintainingspecified wall thicknesses during draws previous to the last draw.

In these so-called breakdown draws the greatest possible reduction ofthe crossl sectional area of the tube in each draw is sought in order tominimize the total number of draws required to produce a finished tubefrom a given starting size.

Wear occurs in the die which forms the outside diameter, therebyallowing an increase in both the outside diameter and wall thickness. Bychanging the position of the tapered plug so that a correspondinggreater inside diameter is produced, the wall thickness is brought backto its specified value thereby assuring the proper reductions in crosssectional area.

Because the tapered nose allows not only distribution of wear of theplug itself but also compensation for die wear, the use of the taperedplug is very widespread in the non-ferrous tube field. The straight ornon-tapered plug finds much less frequent application being used mostlyin finish draws, in which compensation for die wear is not a factor.Added life for both types of plugs can be obtained by using tungstencarbide for the nose.

However, both the straight and tapered plugs have two maindisadvantages. First, because the plugs are positioned by rods, theyobviously cannot be used for drawing of tubes in coil form. Thisprecludes their use in the small tube field in which coils are the usualform. Second, the drawing of relatively long tubes in straight lengthstends to produce surface defects known as chatters. A long rod willstretch more under a given tension than a short rod. Unless the frictionbetween the tube and the plug is quite uniform (which is unusual inactual drawing) the changes in friction cause variations in rod tensionwhich in turn produces varying amounts of stretch in the plug rod. Thisvariation in stretch causes slight changes in the position of the plug(an oscillation) producing a series of visible circumferential rings ofvariable wall thickness in the tube. This has become a serious problemparticularly in the drawing of long copper tubes (up to l2() feet) forradiation heating.

The defects of chatters in drawing bars, steel, aluminum and othermetals can also be avoided by the use of floating plugs.

Tube drawing may be done by conventional floating plugs having astraight nose of uniform diameter and a tapered shoulder which makes theplug self-positioning and eliminates the need for a plug rod. Thefriction between the tube, and nose tends to carry the plug along withthe tube but is balanced by the bearing of the shoulder against theinside surface of the tube. Floating plugs are particularly adaptable tothe drawing of tubes in coil form and have been used in this field for anumber of years. More recent applications have been made on the drawingof tubes in long straight lengths, principally to eliminate chatter andto reduce machine set-up time. Floating plugs will eliminate chattersince the self-positioning effect of the plug eliminates tension of theplug rod and consequent chatten When used to draw straight lengths,floating plugs are usually attached to plug rods to facilitate theinsertion of the plug in the tube. The rod is loosely attached to thedrawbench and has no positioning effect.

The conventional floating plug has one major disadvantage. Since theplug is of one-piece construction and the shoulder of the plugdetermines its position, only a limited area of the nose can beutilized. Therefore, distribution of wear overY thenose and the use of atapered nose to produce dimensional changes and to compensate for diewear are impossible. This results in short service life for both plugsand dies. Present attempts to counteract this disadvantage consist ofthe use of solid tungsten carbide plugs and the grinding back of theshoulder in successive steps to produce additional nose area. Thisremedy is costly both in time and material.

Another disadvantage is that dies and plugs must be matched forsuccessful drawing. The shape of the mouth of the die must be such thatthe tube in following the contour of the die forms a suitable insidesurface against which the shoulder of the plug bears. Unless the diecontour and shoulder contour follow a definite relationship, breaking ofthe tube occurs.

In spite of these serious disadvantages tube manufacturers are forced touse conventional oating plugs because they are the only type that can beused for coil drawing and because, at present, they are the onlyconsistent remedy for chatter in long straight lengths.

It is accordingly a principal object of the present invention to providean adjustable floating plug which eliminates the disadvantages connectedwith conventional floating plugs and which also incorporates most of theadvantages of both conventional floating plugs and cornmon drawingplugs.

It is another object of the present invention to provide an adjustablelloating plug wherein the shoulder portion can be easily and accuratelymoved relative to the nose of the plug and can be positively locked inthe desired position.

It is another object of the present invention to provide an adjustablefloating plug of the type having a nose of uniform diameter wherein wearcan be distributed over the entire nose.

It is another object of the present invention to provide an adjustablefloating plug o-f the type having a tapered nose wherein distribution ofwear, adjustment for dimensional tolerances and compensation for dieWear can be achieved.

lt is still another object of the present invention to provide anadjustable lloating plug wherein a proper combination of thread pitchand nose taper allows rapid and accurate adjustment of the adjustablefloating plug.

lt is still another object of the present invention to provide anadjustable iioating plug wherein a nose of wear resisting tungstencarbide can be inserted to increase plug life.

It is still another object of the present invention to provide anadjustable floating plug having a shoulder which makes the plugself-positioning, making it adaptable for drawing of tubes in coil form.

It is still another object of the present invention to provide anadjustable floating plug wherein the selfpositioning effect of theshoulder eliminates chatter in the drawing of tubes in straight lengthsand wherein the self-positioning effect reduces materially machineset-up time.

It is still another object of the present invention to provide anadjustable floating plug which can be easily attached to drawbench plugrods to facilitate the insertion of the plugs into the tube beforedrawing, although the rod is not needed for positioning the plug duringdrawing.

It is still another object of the present invention to provide anadjustable floating plug including an interchangeable assembly ofshoulder sleeves and plug bodies which allows maximum exibility inmatching dies and plugs, reduces machine time lost in reconditioning ofplugs and reduces overall tool maintenance costs.

For other objects and a better understand of the invention, referencemay be had to the following detailed description taken in connectionwith the accompanying drawin gs, in which:

Figure l is a central longitudinal sectional view portion of a drawbenchconstruction, its die and tubing being drawn, and shows the adjustablefloating plug construction in operative use therein;

Fig. 2 is a similar view of a modified form of drawing plug showing acarbide nose.

Fig. 3 is an exploded perspective view of the parts comprising theadjustable floating plug;

Fig. 4 is a transverse sectional view taken along the line 4-4 of Fig.3; and

Fig. 5 is a view similar to Fig. 1 and showing a still further modifiedform of drawing plug.

Referring now more in detail to the drawing, in which similar referencenumerals identify corresponding parts throughout the several views,there is shown an adjustable floating plug, referred to collectively as10, and including a drawing plug 11 of hardened tool steel,substantially as illustrated.

In machinery that is used to draw tubing, it is generally the practiceto pull the tubing 12 through an opening between the outside of thedrawing plug 11 and the inside of the die 13. Since the tube drawingmachinery is well known and understood by those skilled in the art, itis not believed that an elaborate discussion of the tube drawingmachinery is necessary. Therefore, the drawing and description will beconfined to the adjustable floating plug itself, and which comprises thepresent invention.

The drawing plug 11 consists of a tapered nose 14 integral with a smoothcylindrical portion 15. The intermediate portion 15 on its face remotefrom the tapered nose 14 is integrally formed with a smooth cylindricalportion 16 of lesser diameter and which continues in an elongated,externally threaded shank 17, substantially as illustrated.

Countersunk openings 18 and 19 are provided in opposite ends of thedrawing plug 11, for a purpose which will be clear to those skilled inthe art.

An adjustable shoulder sleeve, referred to collectively as Ztl, isprovided at one end with a smooth internal bore 21, adapted to slidablyreceive the intermediate portion 15 of drawing plug 11, as shown in Fig.l. The sleeve 20 is also provided at its other end with an internallythreaded bore 22, communicating with and of lesser diameter than thebore 21 and adapted to receive the externally threaded shank 17, also asshown in Fig. 1. The sleeve 20 is also provided on opposite sides withwrench flats 23 to facilitate adjusting of the sleeve 20 relative to theplug 11.

The sleeve 20 is formed of the same hardened tool steel as plug 11, andis bevelled as at 24 at the end thereof receiving the tapered nose 14.The trailing edge of sleeve 20 is circumferentially chamfered, as at 25.

A lock nut, referred to collectively as 25' is provided with aninternally threaded bore 26 adapted to receive the externally threadedshank 17, as shown in Fig. 1, one face of lock nut 25 abutting theadjacent face of sleeve 20 and locking the position of the latterrelative to the tapered nose 14. The lock nut 25 is provided with wrenchflats 27 to facilitate locking. The opposite ends of lock nut 25 arecircumferentially chamfered, as at 28 and 29.

The tapered portion 24 of above 20 is ground while the intermediateportion 15 and tapered nose 14 of plug 11 are ground and chrome plated.

Thus, the above three-piece construction allows the shoulder 24 to bemoved relative to the tapered nose 14 and to be locked securely in adesired position. The threaded connection between the plug body 11 andshoulder sleeve 20, as illustrated in the drawing, is the most accurateand positive means of relative motion but other means of locking andadjusting may be used, as will be obvious to those skilled in the art.

Because the shoulder 24 is movable, the area of contact between theinside of the tube 12 and the plug nose 14 can be shifted. With thetapered nose 14, the shoulder position can be changed to produce smallchanges in the inside diameter in order to meet dimensional tolerancesfor inside diameter or wall thickness; to compensate for die 13 wearduring breakdown draws, or to distribute wear on the nose 14. These willbe remembered as the chief advantages of common drawing plugs.

Because of the shoulder 24, the adjustable floating plug retains theadvantage of the conventional floating plug. Being self-positioning, itreduces machine set-up time and eliminates chatter in the drawing oflong straight lengths and light wall tubing of any length. In addition,it can be used in the drawing of tubes in coil form.

As with conventional floating plugs the shoulder angle of the adjustablefloating plug 10 and the mouth angle of die 13 must be matched forsuccessful drawing. However, with the adjustable floating plug severalshoulder sleeves of different shoulder angles can be used with one plugbody 11 allowing the use of different dies 13 with the substitution ofshoulder sleeves 20 until the most satisfactory shoulder angle is found.Several plug bodies 11 may also be used with only one shoulder sleeve 20to reduce the original cost and to eliminate loss of production timewhen one plug body requires polishing, plating or other reconditioning.This flexibility is not found in conventional floating plugs.

The design of the adjustable floating plug 10 also permits easy andaccurate adjustment. For example, the combination of a 16 pitch threadon the connection between the shoulder sleeve 20 and plug body 11 with anose 14 taper of 0.016 on diameter per inch of length will result in achange of 0.001" in the inside diameter (and 0.005 in the wallthickness) of the drawn tube 12 when the shoulder sleeve 20 is rotated afull turn (360 degrees) around the plug body 11. This featurefacilitates final adjustment of the shoulder sleeve position after themeasurement of several tubes drawn with the preliminary adjustment.Other combinations of taper and standard threads are, of course,possible.

Referring now particularly to Fig. 2, there is shown a modified form ofdrawing plug, referred to collectively as 11a, adapted to be used inconnection with the shoulder sleeve 20 described above. In this form atungsten carbide nose piece 14a is inserted for incorporation in thedrawing .plug 11a to increase wear resistance. The tapered nose 14a isprovided at its inner end with a conical formation 30 which is receivedwith a correspondingly shaped conical opening 31 provided inintermediate portion 15a, substantially as illustrated and securedtherewithin by suitable bonding material. This type of insert has beenused frequently in common drawing plugs and has proven an advantage insizes up to 11/2 in diameter. In larger sizes, the economic advantagehas not been determined.

In other respects the form of the invention shown in Fig. 2 is the sameas that shown in Figs. l through 4, and like reference numerals identifylike parts throughout the several views.

Referring now to Fig. 5, there is shown a still further modified form ofdrawing plug, referred to collectively as 11b, and differing from theplug 11 in the provision of a straight nose 14b coterminous with theintermediate portion 15. Because the shoulder sleeve and shoulder 24 ismovable, the area of contact between the inside of the tube 12 and thenose 1411 can be shifted, distributing in the wear over the entire nose14b by successive changes of shoulder position.

In other respects the form of the invention shown in Fig. 5 is the sameas that shown in Figs. l through 4, and like reference numerals identifylike parts throughout the several views.

Shoulder sleeve 20 as seen in Figure 3 may have an outer portion ofcarbide at a conventional brazed joint as indicated by numeral 20a.

Actual use of adjustable floating plug 10 has been made in the finishdrawing of copper water tube in forty foot lengths. This draw reducedtubing of 'MU' outside diameter with 0.0045 wall thickness to a finishedsize of outside diameter 0.040" wall thickness (designated by theplumbing trade as 1/2 Type L copper water tube) a reduction of crosssectional area of approximately 32%. This size was chosen because it istypical of the sizes most frequently required in installations forradiant heating. The demand for long lengths for this application hasled to the use of long drawbenches and the use of floating plugs toeliminate chatten The same demand for long lengths has also led to theexperimental drawing of copper tubes in coil form on drawblocks similarto those used in heavy wire drawing. It has already been pointed outthat only floating plugs can be used in this form of drawing.

The extension of the use of adjustable floating plugs into other sizeranges is certain. In the smaller ranges the drawing of tubes in coilform is prevalent particularly in the so-called small tube mills.Conventional floating plugs are already used in these plants. Inaddition, the problem of chatter in the drawing of straight lengthsbecomes progressively more serious as the tube size decreases regardlessof the length involved. In this field conventional floating plugs havehad limited application as a solution because of their short life.However, the adjustable floating plug 10, which eliminates the economicdisadvantages of the conventional floating plug, should receive a morefavorable reception. In the direction of larger sizes, the use ofadjustable floating plugs will depend upon their ability to reducemachine set-up time. The present trend for breakdown draws is to usemultiple drawbenches, usually employing three dies and six plug rods,requiring six preliminary adjustments and six final adjustments of plugposition, when common drawing plugs are used. The use of adjustablefloating plug 10 can eliminate the preliminary adjustment time but thisadvantage must be balanced against the higher first cost of adjustablefloating plugs as compared to common plugs.

While various changes may be made in the detail construction, it shallbe understood that such changes shall be within the spirit and scope ofthe present invention, as defined by the appended claims.

I claim:

l. An adjustable floating plug for tube drawing cornprising a plug body,including a nose adapted to size the inside diameter of the tube, ashoulder sleeve adjustable along said body plug and including a taperednose portion, and means for locking the position of said shoulder sleeverelative to said plug body.

2. An adjustable floating plug for tube drawing comprising a plug body,said plug body including a nose portion adapted to size the insidediameter of the tube and an externally threaded shank, an adjustableshoulder sleeve having a smooth internal bore at one end adapted toreceive said nose portion of said body plug and an internally threadedbore at the other end communicating with and of substantially lessdiameter than said smooth bore, said internally threaded bore beingadapted to receive said externally threaded shank, and an internallythreaded lock nut adjacent the end of said sleeve and adapted to bescrewed on to said threaded shank.

3. An adjustable floating plug for tube drawing comprising a plug body,said plug body consisting of a smooth cylindrical intermediate portion,a substantially cylindrical nose portion adjacent said intermediateportion and an elongated, externally threaded shank adjacent the otherend of said intermediate portion, said nose portion being adapted tosize the inside diameter of the tube being drawn, an adjustable shouldersleeve having a smooth cylindrical bore adapted to receive saidintermediate portion at one end, said sleeve at the other end having aninternally threaded bore of lesser diameter than and communicating withsaid smooth bore and adapted to receive said threaded shank, said sleeveat the end adjacent said nose portion being inwardly tapered and meansfor locking the position of said sleeve relative to said nose portion.

4. An adjustable floating plug according to claim 3, said meanscomprising a lock nut screwed on to said threaded portion adjacent theend of said sleeve remote from said nose portion.

5. An adjustable oating plug for tube drawing cornprising a plug body,said plug body consisting of smooth, substantially cylindricalintermediate portion, a substantially cylindrical, tapered nose integralwith and adjacent one end of said intermediate portion, and an elongatedexternally threaded shank integral with and adjacent the other end ofsaid intermediate portion, an adjustable shoulder sleeve having at oneend the smooth internal bore adapted to slidably receive saidintermediate portion and at the other end an internally threaded borecommunicating with and of less diameter than said smooth bore andadapted to receive said threaded shank, and means for locking saidsleeve relative to said tapered nose.

6. An adjustable floating plug, according to claim 5, said meanscomprising an internally threaded lock nut adapted to be screwed on tosaid externally threaded shank adjacent the end of said sleeve remotefrom said nose portion.

7. An adjustable floating plug for tube drawing comprising a plug body,said plug body consisting of smooth, substantially cylindricalintermediate portion, a tungsten carbide nose piece connected to one endof said intermediate portion and an elongated externally threaded shankintegral with the other end of said intermediate portion, an adjustableshoulder sleeve having a smooth internal bore at one end adapted toslidably receive said intermediate portion and having an internallythreaded bore at the other end communicating with and of less diameterthan said smooth bore, and adapted to receive said threaded shank, andmeans for locking the position of said sleeve relative to said nosepiece.

8. An adjustable floating plug according to claim 7, said meanscomprising a lock nut having an internally threaded bore adapted toreceive said externally threaded shank.

9. An adjustable oating plug for tube drawing comprising a drawing plugof hardened tool steel, said plug consisting of a smooth, substantiallycylindrical intermediate portion, a nose portion adjacent one end ofsaid intermediate portion and integral therewith, said nose portionbeing adapted to size the inside diameter of the tube being drawn, andan elongated externally threaded shank integralvwith the other end ofsaid intermediate portion and of less diameter than said intermediateportion, an adjustable shoulder sleeve of hardened tool steel having atone end a smooth internal bore adapted to slidably receive saidintermediate portion and at the other end having internally threadedbore communicating with and of less diameter than said smooth bore andadapted to receive said threaded shank, said sleeve at its end adjacentsaid nose portion being inwardly bevelled, and means for locking saidsleeve relative to said nose portion.

10. An adjustable oating plug according to claim 9, said nose portionbeing tapered inwardly away from said intermediate portion.

11. An adjustable oating plug according to claim 10, said nose portionbeing substantially cylindrical and of uniform diameter.

12. An adjustable floating plug according to claim 10, said nose portionbeing formed of tungsten carbide.

13. An adjustable floating plug for tube drawing according to claim 10,said means for locking said sleeve comprising a hardened tool steel locknut adapted to be screwed on to said externally threaded shank adjacentthe end of said sleeve remote from said nose portion.

References Cited in the le of this patent UNITED STATES PATENTS1,511,091 ORourke Oct, 7, 1924 2,025,439 Brownstein Dec. 24, 19352,173,099 Dennis Sept. 19, 1939 2,285,539 Staples June 9, 1942 2,355,734Katz Aug. 15, 1944 2,359,339 Wadell Oct. 3, 1944 2,473,383 MessingerJune 14, 1949 FOREIGN PATENTS 458,737 Great Britain Dec. 24, 1936

